The manufacture of products normally involves monitoring production by taking and examining random samples from the flow of products. Sample copies can generally be removed from an unorderly product flow without special restrictions. However, in an orderly product flow, the degrees of freedom for removing the sample copy are significantly reduced, particularly since the removal of the sample copy must not disturb the order of the product flow during the sample removal.
The problems with conventional systems are particularly acute in rapidly performed production processes. Due to their high output, intermediate buffer storage cannot be provided in rapidly performed production systems so that strict synchronism must be maintained.
The transfer of semi-finished and finished products from station to station is greatly dependent on the working cycle. For orderly product flow, a disturbance to the order in one station is conveyed downstream in the operation at the speed imparted by the working cycle of the process to that point. Such disturbance causes a buildup of material. Based on experience, this buildup only lasts a few seconds, and it is unnecessary to stop the process temporarily for removal of the accumulation.
In the orderly material flows in the production of printed products, an order is established that permits the individual products to be picked up separately. Disturbances in the order of the material flow adversely affect the synchronism and can cause serious accumulations of material. Thus, interferences in fast stream flows are always critical to the processes.
For example, a rotary printing system has a standard output of 50,000 to 100,000 copies per hour. In such system, a sample copy should be removed as quickly as possible after the copy has been printed. Preferably, the removal of the sample copy should not interfere with the stream flow in the critical processing section between delivery and the individual picking up. Thus, the sample copies are removed from a less critical processing section in conventional systems.
At rotary printing production speeds, deficiencies must be detected and corrected early. Otherwise, thousands of faulty copies will be produced. Thus, it is desirable to minimize the time between production of an individual product and its examination.